[tex]$ \ $Consideram $f(x) = ax+b$ \\ \\ $ f(2-3x) = 6x-8 \Rightarrow a(2-3x) + b = 6x-8 \Rightarrow \\ \Rightarrow 2a-3ax +b = 6x-8\Rghtarrow \Rightarrow-3ax +2a+b = 6x-8 \Rightarrow \\ \ \\\Big\{ -3a = 6 \quad $ si $ \quad 2a+b = -8\Big\} \Rightarrow \\ \\ \Rightarrow \Big\{ a = -2 \quad $ si $ \quad 2\cdot(-2) +b =-8\Big\} \Rightarrow \\ \\ \Rightarrow \Big\{ a = -2 \quad $ si $ \quad b = -4\Big\}[/tex]
[tex]\Rightarrow \boxed{f(x) = -2x-4}[/tex]
